IOCAN

# Analog Input

## Overview

An **Analog Input** reads an analog voltage on a hardware pin and converts it into a

scaled engineering value. It is the most common input type — used for any

voltage-output sensor such as temperature (NTC), pressure, throttle/pedal

position, fuel level, and similar.

The raw measured voltage is mapped to an output value using the input/output

two-point scaling below. For a non-linear sensor, feed this input into a

[Map Input](Map_Input) for multi-point scaling.

## Prerequisites & hardware

- A sensor whose output is a **voltage** within the selected range.

- Wire the sensor signal to the chosen analog pin and its ground to controller ground.

- Pick the **range** to match the sensor's full-scale voltage so you use the full

  ADC resolution.

- **Pull-up:** most analog pins have **no pull-up hardware**, so the option is

  unavailable on the majority of inputs. Where a pin does support it, a resistive

  sensor (e.g. an NTC thermistor) can use it to form a divider instead of an

  external resistor. Otherwise, fit the divider externally.

## Add it in the app

1. Add a new input and choose **Analog Input** as the type.

2. Select the **pin** the sensor is wired to.

3. Give it a clear **alias** (e.g. `Oil Temp`).

4. Set the **range**, scaling and fault thresholds below.

5. For a non-linear sensor, scale it with a [Map Input](Map_Input).

## Settings reference

> Schema: `config/AdcConfiguration.proto`.

| Setting | Meaning | Unit | Range / values | Notes |

|---|---|---|---|---|

| **Range** | Input voltage range / scaling reference | — | `5 V`, `Internal 5 V`, `12 V`, `Raw` | Choose the smallest range that covers the sensor's full-scale voltage. `Raw` reports unscaled ADC counts. |

| **Pull-up** | Enables an internal pull-up on the pin | — | on / off | **Only available on pins with pull-up hardware** — most analog pins do not have it. Where present, lets resistive sensors (e.g. NTC) form a voltage divider. |

| **Low-pass filter** | Smooths a noisy signal | — | on / off | Reduces jitter; adds a small amount of lag. |

| **Saturation** | Clamps the output to the out min/max range | — | on / off | When on, values are limited to `Out min … Out max` instead of extrapolating. |

| **Enable interpolation** | Linearly interpolates between the in/out scaling points | — | on / off | Off = step/clamped mapping. |

| **In min / In max** | Raw input range to scale **from** | mV (raw counts if `Raw`) | sint32 | The measured low/high points. |

| **Out min / Out max** | Engineering range to scale **to** | input unit | sint32 | The value reported at In min / In max. |

| **Fault min / Fault max** | Out-of-range thresholds that flag a fault | mV | sint32 | Readings outside this band indicate an open/short or failed sensor. |

**Scaling:** the input is mapped from `In min…In max` to `Out min…Out max` using

[two-point interpolation](Scaling_and_Maps#two-point-interpolation).

For example, a 0.5–4.5 V pressure sensor reading 0–10 bar: set In min/max to the

voltages and Out min/max to `0`/`10`. Non-linear sensors should instead pass this

input through a [Map Input](Map_Input) for

[multi-point scaling](Scaling_and_Maps#multi-point-scaling).

## Common settings

Analog Input also uses the shared settings — alias and pin. See

[Common IO Settings](Common_IO_Settings).

## Example — coolant temperature (NTC)

1. Type **Analog Input**, alias `Coolant Temp`, on the sensor's pin.

2. Range `5 V`. If the pin has pull-up hardware, **enable Pull-up** to form the

   divider with the NTC; otherwise fit the divider resistor externally.

3. **Low-pass filter on** (temperature changes slowly; suppress noise).

4. Feed this input into a [Map Input](Map_Input) with a voltage → °C curve from

   the data sheet (NTCs are strongly non-linear, so a two-point scale is not enough).

5. Set **Fault min/max** just inside the supply rails to catch an open or shorted

   sensor.

## Troubleshooting

- **Reads full-scale or zero / stuck:** check wiring; the value may be sitting

  outside the **Fault min/max** band (open or shorted sensor).

- **Value noisy / jumpy:** enable the **Low-pass filter**.

- **Reading scales wrong:** verify **In min/max** are in the same units as the

  measured signal and that **Range** matches the sensor.

- **Non-linear / offset reading:** scale it with a [Map Input](Map_Input) rather

  than the straight in/out scale.

## Related

- [Analog Switch Input](Analog_Switch_Input) — multi-position switch on one

  analog pin.

- [Map Input](Map_Input) — multi-point scaling for non-linear sensors.

- [Scaling & Maps](Scaling_and_Maps)